Prepare the crust first: Place flour, sugar and salt in a food processor and pulse a couple times to combine. Add the cold, cubed butter and pulse until no large chunks of butter remain.
2 1/2 cups flour, 2 Tbsp. sugar, 1 tsp. salt, 1 cup unsalted butter, cold, cubed (16 Tbsp.)
Slowly stream in the cold buttermilk until the dough comes together. At first, it may look dry and crumbly but continue running the food processor, it will be enough to bind the dough and it will come together!
1/2 cup buttermilk, cold
Turn dough out onto a lightly floured surface and gently knead/form dough until it comes together. Divide dough into 2 equal pieces. Form into a semi-flat thick oval shape, wrap in plastic wrap and place in the fridge for at least 30 minutes, or up to 3 days.
In a large Dutch oven or large deep pan, melt the butter. Add the onions, carrots, celery and garlic.
4 Tbsp. unsalted butter, 1 small white onion, about 1 cup, chopped, 3 medium carrots, peeled and small dice, 3 stalks celery, chopped, 3 cloves garlic, minced
Saute over medium heat until fragrant and soft, about 8 minutes. Season with salt and pepper.
1 tsp. salt, 1/4 tsp. black pepper
Add flour and stir to coat all of the vegetables.
1/4 cup flour
Add diced ham and stir to combine.
2 heaping cups ham, chopped into small cubes/pieces
Add broth and milk and bring to a boil, then down to a simmer and cook until a thick creamy consistency, about 5-7 minutes.
1 1/4 cup whole milk, 1 cup chicken or vegetable broth
Add peas, apple cider vinegar and fresh herbs. Stir to combine. Taste and adjust seasonings, adding more salt or herbs as desired. Remove from heat & allow to cool while you prepare the crust.
1 cup frozen peas, do not thaw, 1 Tbsp. apple cider vinegar, 1/2 cup fresh herbs, chopped. I like using sage, thyme, rosemary and parsley
Preheat the oven to 375°F. Roll out one of the disks of dough. Roll into a large circle (about 12 inches) on a lightly floured surface and carefully transfer to a 9” pie dish.
Optional step by partially blind bake the bottom crust: Freeze the dough for 15-30 minutes to keep the dough nice and chilled, this will solidify the fat, which helps prevent shrinkage. Line dough with parchment paper & fill with pie weights to help keep the edges from sagging as crust bakes* Bake the pie crust for ~15-20 minutes just until edges are set and lightly brown.
If not partially blind baking the crust: Spoon the cooled filling onto the crust. Roll the second disk of pie dough out on a floured surface and carefully place over the pie filling. Fold the excess dough behind the bottom crust then crimp the 2 pie crusts together to seal.
Use a small knife to make a couple small slits in the center of the top crust (to allow steam to escape while it bakes).
Use a pastry brush to brush the crust and edges with a beaten egg.
1 large egg, beaten for egg wash
Bake for at least 35-40 minutes or until crust is golden brown. Use foil on the edges or a pie crust shield to protect edges from browning too much, if necessary.
Allow to rest for at least 15 minutes before slicing and serving.